1. Field of Invention
The present invention relates to a method of preparing a water-soluble and biodegradable antimicrobial agent, and more particularly, the present invention relates to a method of preparing a polypeptide chloride containing N-halamine groups.
2. Description of Related Art
In our living environments, even on the human body, the presence of at least thousands of microorganisms can be found. Among the microorganisms, some are beneficial to humans and some are harmful. Beneficial microorganisms can be used to produce desired foods or chemicals, and harmful microorganisms may destroy foods or drugs in processing, storage and transportation, or in use by consumers, or even cause an infection of tissues in body. Thus, in order to avoid the potential harms by such microorganisms to humans, there exists the need for antimicrobial agents in our living environments and various applications. It is currently known that many antimicrobial agents have been developed and widely used in various living applications.
Among currently developed antimicrobial agents of various types, there is a class of antimicrobial agent containing an N-halamine compound as a component, which has excellent antimicrobial efficacy for bacteria, molds and viruses and the like. It is known that an N-halamine compound refers to a compound containing a halamine functional group of N—X (X may be Cl, Br, or I), which can be obtained by oxidation of a compound containing a functional group, such as amine, amide, or imide group, with an oxidant (for example, hypohalites). The N—X functional group in this type of compounds can slowly dissociate by the action of water molecules in water in the presence of microorganisms, to release oxidizing halogen ions, while the N—X functional group in this compound is reduced to an N—H functional group. The released oxidizing halogen ions can kill microorganisms such as bacteria and molds. After the N-halamine compound dissociates into the halogen ion to kill the microorganisms, it usually can be treated with the hypohalites above again, so that the N—H functional group thereof can be oxidized into the N—X functional group again, thereby causing the regeneration of the sterilization function. It is known that the N-halamine compound is very useful for disinfection in family, commercial and medical places, due to having the advantages such as fast sterilization speed, high sterilization efficiency, long duration, good stability, and regeneratability of antimicrobial capability.
The research by Worley is the most representative of all the development of conventional antimicrobial N-halamine compounds. The research group leaded by Worley has developed many kinds of N-halamine compounds having antimicrobial property. However, all of these compounds are based on a cyclic N-halamine compound, and the structures disclosed are, for example, oxazolidinones (U.S. Pat. No. 5,902,818), imidazolidinones (U.S. Pat. No. 5,126,057), hydantoins, and spirocyclic amines, and the like. All of these structures are treated with hypochlorites to yield the N—Cl functional group, thereby having the antimicrobial efficacy; however, whether for these monomers or the polymer, the problem of less solubility in water exists, such that its application fields, even antimicrobial property, are limited.
On the other hand, based on the protection of environment, antimicrobial agent systems nowadays mostly tend to use an aqueous system instead of an organic solvent, thereby reducing the harms by the organic solvent to the environment.
In order to be applicable in the aqueous system, Worley et al considered that a hydrophilic group can be attached onto a side chain of the polymer to obtain an antimicrobial substance having high water solubility. A quaternary ammonium salt is generally used as the hydrophilic group, thereby improving the solubility in water. For example, Worley et al has developed an antimicrobial polymer in which siloxane is used as the skeleton and a cyclic N-halamine compound hydantoin and quaternary ammonium salt structures are attached thereon, respectively (U.S. Pat. No. 7,335,373). Therein, both siloxane and hydantoin have very poor solubility in water, and the water solubility of the antimicrobial polymer is improved mainly by the quaternary ammonium salt, which has no antimicrobial efficacy, and therefore, a longer contact time is required for such an antimicrobial agent to achieve the sufficient antimicrobial effect. Although Worley et al has designed this antimicrobial polymer structure by improving the water solubility of the cyclic N-halamine compound, the problem that it is not totally soluble in water still exists and a small amount of alcohols still needs to be added to help to dissolve the antimicrobial polymer for using the cyclic N-halamine compound. However, this cannot completely resolve the doubts about the likely harms caused by the organic solvent to the environment. On the other hand, the structure of this antimicrobial polymer is obtained by the chemical synthesis, and during and after the synthesis, organic solvents may be used more or less and unnecessary side-products may be generated, thus, the harms caused to the environment may also occur in the manufacturing process to some extent. Furthermore, a special synthesis via multiple preparation processes is needed for such an antimicrobial polymer, which would thus be expensive. This can be confirmed by the fact that techniques for preparing such compound had been disclosed by Worley et al many years before, but up to now, no numerous products have been marketed.
Therefore, it is necessary to develop a water-soluble and antimicrobial substance having biocompatibility, non-toxicity, regenerative antimicrobial capability, easy preparation, and low cost.